Window sash balance



y 1957 F. J. DECKER ETAL 2,797,435

WINDOW SASH BALANCE Filed Jan. 18, 1954 Inventor's fiedenck 1T. De\(e.\"

Mia-f2 Gregg H b is Attorney.

2,791,435 WINDOW SASH BALANCE Frederick J. Decker, Elmira, and Mahlon H.Gregg, Rochester, N. Y., assignors to The Caldwell ManufacturingCompany, Rochester, N. Y., a corporation of New York Application January18, 1954, Serial No. 404,575 3 Claims. (Cl. 16-198) The presentinvention relates to counterbalancing devices, and more particularly, tosuch devices utilized in conjunction with window sashes.

In window-sash balances, it is desirable to counterbalance, as closelyas possible, the weight of the window at all positions thereof. This isdesirable in order that the same amount of force is required to move thewindow at the beginning of its travel as at the end of its travel. Inmost spring-operated sash balances, an equal counterbalancing effect isdifficult to obtain because, as the spring is compressed, a greaterforce is exerted on the window. This occasions difficulty in thecounterbalancing of a window, since, if the window is exactlycounterbalanced at the beginning of its travel it is over-compensated atthe end of its travel, and hence is difficult to move. While, if thewindow is counterbalanced for the end of its travel, it moves up tooreadily at the beginning of its travel and under some conditions, maynot stay closed.

Accordingly, it is a principal object of the present invention toprovide a window-sash balance wherein the counterbalancing effect is ofapproximately equal value at both the beginning and end of the windowtravel.

Another object of the present invention is to provide a spring-operatedsash balance wherein the varying force exerted by the spring iscounteracted by a variation of friction within the sash balance.

A further object of the present invention is to provide an improvedwindow sash balance which is simplified, economical, and compact inconstruction.

The features of this invention which are believed to be novel are setforth with particularity in the appended claims. The invention itself,however, both as to its organization and method of operations, togetherwith further objects and advantages thereof, may best be understood byreference to the following description when taken in connection with theaccompanying drawings wherein:

Fig. 1 is a front view, partly cut away, of a device embodying theprinciples of the present invention when mounted for use;

Fig. 2 is a perspective view of a device embodying the principles of thepresent invention;

Fig. 3 is a cross-sectional view of the devices illustrated in Fig. 2,and

Fig. 4 is a view taken along line 44 of Fig. 3.

In the drawings, a sash balance embodying the principles of the presentinvention is therein designated by the general reference numeral 11. Thesash balance 11 comprises a casing 13 made of any suitable material,such as metal. The casing 13 is generally cylindrical in shape andincludes a back plate 15 and a removable front plate 17 (Fig. 4). Thecasing 13 together with the front plate 15 and the back plate 17 form anaperture 19. The casing 11 is fastened to a window frame 23 by anysuitable means, here shown as base plate 21 mounted on the window frame23 by screws 25.

A spool 27 is slidably positioned within the aperture 19, that is, thespool 27 floats in the aperture 19 and is nited States PatentO PatentedJuly 2, 1957 not mounted on a fixed center of rotation such as a shaftor an axle. The spool 27 is preferably constructed of a material havinga relatively high coeflicient of friction, such as plastic or suitabletypes of glass.

A center post is rotatably mounted on the back plate 15 and extends intothe aperture 19. A coil spring 31 is positioned within the spool 27 andis concentric with the post 35. End 32 of the spring 31 is attached tothe spool 27 and end 33 of the spring 31 is attached to the center post35. The spring 31 urges the spool 27 in one direction, here shown ascounterclockwise.

A flexible band 37 of suitable material, such as metal, is wound arounda groove 40 (Fig. 4) in the outer edge of the spool 27. The band 37 iswound around the spool 27 in a direction so that the spool 27 is turnedagainst the force of the spring 31 when band 37 is unrolled from thespool 27. As shown, the band 37 is wound to turn the spool 27 in aclockwise direction when unrolled therefrom because of theaforementioned normal counterclockwise urging of the spool 27 by thespring 31.

A tensioning arm 39 is attached to the center post 35 for adjusting theforce exerted by the spring 35. As mentioned above, the post 35 isrotatably mounted on the plate 15. Therefore, when the arm 39 isrotated, the post 35 .also rotates. For example, if it is desired toincrease the force exerted by spring 31 the arm 39 movescounterclockwise, thus, tightening the spring 31. The arm 39 is held inplace by stops 41.

Inoperation, the band 37 is attached to one side of a window sash and asimilar band is attached to the other side of the sash, thereby tosupport the weight of the window between them. When the window is in aclosed position, the band 37 is unwound from the spool 27 and the spring31 is tightly coiled and a relatively large counterbalancing force isexerted by the spring 31. When the window is open, the spring 31 isloosely coiled and a smaller force is exerted thereby. However, asmentioned above, the spool 27 floats in the aperture 19. Therefore, whenthe window is down and the spring 31 is uncoiled, the rim of the spool27 is forced into frictional engagement with the casing 13, thus makingthe rotation of the spool 27 more difiicult and increasing the totalcounterbalancing force exerted on the window. When the window is raisedand the spring 31 is coiled, the spool 27 is retracted by the coiling ofthe spring 31 and is not in frictional engagement with casing 13. Hence,there is no increase in the total counterbalancing force exerted on thewindow as there is when the window is closed. However, as mentionedabove, when the spring 31 is tightly coiled, a greater counterbalancingforce is exerted by the spring than when the spring 31 is looselycoiled. Therefore, because of the increased force when the window islowered caused by the frictional engagement of the spool 27 with thecasing 13, the total counterbalancing force exerted at the beginning ofwindow travel is equal to the total counterbalancing force at the end ofwindow travel. This equality of counterbalancing forces enables thewindow to be smoothly and easily raised and lowered.

While a specific embodiment of the present invention has been shown anddescribed, it will of course be understood that various modificationsmay be devised by those skilled in the art which will embody theprinciples of the present invention and found within the true spirit andscope thereof.

What is claimed is:

l. A counterbalance for window sashes comprising a cylindrical casinghaving a back plate and a removable front plate, said plates and saidcasing forming a cylindrical aperture, a spool slidably and rotatablypositioned Within said aperture, said spool being of substantially thesame diameter as said aperture, a center post extending into saidaperture, a coil spring positioned within said spool and concentric withsaid center post, one end of said spring being attached to said centerpost and the other end of said spring being attached to said spoolthereby normally urging saidspool in one direction, means foradjustingthe tension of said spring, and a flexible band wound on said spool ina'direction so that when said band is unwound from saidreel the force ofsaid spring opposes the rotation of said spool.

2. A counterbalance for window-sashes comprising a cylindrical casinghaving a back plate and a removable front plate, means for attachingsaid casing to a window sash support, a center postrotatably attached tosaid back plate and extending into said aperture, a spool rotatably andslidablypositioned within said casing, said spool being of substantiallythe same diameter as said casing, a coil spring concentric with saidcenter post and positioned between said center post and said spool tonormally urge said spool in one direction of rotation, one end of saidcoil spring being attached to said center post, the other end of saidspring being attached to said spool thereby to force said spool intofrictional engagement with said casing when said spring is uncoiled andto retract said spool from said frictional engagement when said springis tightly coiled, said spool having a groove, in the edge thereof, anda flexible band wound in said groove in said spool and extendingexternal to said casing for supporting a window sash, said flexible bandbeing wound on said spool in a direction so that said band is unwoundtherefrom against said normally urging of said spring.

3. A counterbalance for window sashes comprising a cylindrical casinghaving a back plate and a removable frontplate, means for attaching saidcasing to a window sash support, a center post rotatably attached tosaid back plate and extending into said aperture, a spool rotatably andslidably positioned within said casing, said spool being ofsubstantially the same diameter as said casing, a coil spring concentricwith said center post and positioned between said center post and saidspool to normally urge said spool in one direction of rotation, one endof said coil spring being attached to said center post, the other end ofsaid spring being attached to said spool thereby to force said spoolinto frictional engagement with said casing when said spring is uncoiledand to retract said spool from said frictional engagement when saidspring is tightly coiled, said spool having a groove in the edgethereof, a flexible band wound in said groove in said spool andextending external to said casing for supporting a window sash, saidflexible band being wound on said spool in a direction so that said bandis unwound therefrom against said normallyurging of said spring, atensioning arm external to said casing and attached to said center postfor adjusting the force exerted by said spring, and stops for retainingsaid tensioning arm in selected positions.

References Cited in the file of this patent UNITED STATES PATENTS703,709 Olmstead July 1, 1902 1,626,018 Wagniere Apr. 26, 1927 1,898,584MantZ Feb. 21, 1933 2,497,279 Steele Feb. 14, 1950 FOREIGN PATENTS22,861 Great Britain Sept. 21, 1895

